Dehydrogenation catalysts



Patented Apr. 15, 1947 UNITED STATES PATE r OFFICE DEHYDROGENATIONCATALYSTS Kenneth K. Kearby, Elizabeth, N. 3., assignor to Standard OilDevelopment Company, a corporatlon of Delaware 5 Claims. i

This application is a division of my prior application Serial No.456,266, filed August 26, 1942, now U. S. Patent No. 2,370,797, issuedMarch 6, 1945.

This application contains a disclosure similar to that contained in theapplication of Kenneth K. Kearby filed February 14, 1942 and assignedSerial No. 430,873, now U. S. Patent No. 2,395,875, issued March 5,1946.

My present invention relates to catalytic dehydrogenation ofhydrocarbons, and more particularly, it relates to improved catalystsfor dehydrogenating olefins and aralkyl hydrocarbons, and to methods forpreparing the said catalysts.

My present invention is particularly adapted to the dehydrogenation oflow molecular weight olefin hydrocarbons having from 2 to 10, preferably2 to 6, carbon atoms, but is also applicable to dehydrogenation ofaralkyl hydrocarbons, such as ethyl and propyl benzene to form, styreneand phenyl, methyl ethylenes, and to convert isopropyl benzene to methylstyrene.

Recently, processes designed to convert butene to butadiene have becomeof increased importance due to the fact that butadiene is an essentialintermediate in one of the more important methods for the production ofsynthetic rubberlike materials.

In the production of diolefins from olefins by the catalyticdehydrogenation of mono-olefins, it is, of course, desirable to obtainas high a yield of the diolefin as possible per one passage of thebutene through the dehydrogenation zone, and as a corollary to thispurpose, it is also a desideratum to this type of process to obtain assmall an amount as possible of by-products. It is also desirable toconduct the dehydrogenation under such conditions that the fouling ofthe catalyst is minimized to as great an extent as possible.

The efilclency of the catalyst is best measured in terms of per centselectivity, which means the per cent of the total amount of initialmaterial which undergoes conversion, which is converted to the desiredproduct. For example, if 50% of the initial material undergoesconversion of some sible to obtain substantially greater yields of thedesired dehydrogenation productth'an can be obtained by the use ofpreviously known catalysts.

- The nature of this new type of catalyst and the 2 conditions underwhich it is used will be fully understood from the followingdescription.

In the above referred to Kearby application, there is disclosed adehydrogenation catalyst which comprises magnesium oxide as a basematerial, iron oxide as an active ingredient, and a small amount of apromoter which consists of an alkali or an alkaline earth oxide. Inaddition, the catalyst may contain a small amount of a stabilizer whichstabilizer may consist of an oxide, of a metal of the right-hand side(transition series) of groups I, II, and III of the periodic system orcertain non-acidic oxides.

As pointed out in the aforesaid prior Kearby application, the principalfunction of the promotor in thes catalysts is to increase thedehydrogenating activity of the catalyst. The principal function of thestabilizer, when used. is to prevent the promoter from volatilizing orbecoming inactive.

Now in my present application, I propose to use as a base, zinc oxide,and this material should constitute the major portion of the entirecatalyst composition. The following table gives the range of eachcomponent which may be used:

Among the alkali metal and alkaline earth oxides which may be used aspromoters, are the oxides of calcium, sodium and strontium, butpotassium oxide is greatly superior.

However, I wish to point out that some of the desired conversion isobtained by omitting the promoter and the stabilizer and compounding thecatalyst only from the base and the active ingredients. The presenceofsilica gel amounting to 1% by weight of the total catalyst containingthe four components mentioned above and silica, improves the activity ofth catalyst.

The following stabilizers give good results: oxides of metals of theright-hand side (transition series) of groups I, II, and III of theperiodic system, particularly oxides of copper and silver, nonacidictransition oxides of chromium, manganese, cobalt and nickel; andnon-acidic oxides of zirconium, cerium, lead, bismuth, and particularlyaluminum and thorium. v

In placeof the iron oxide, manganese oxide and chromium oxide may beused to give good catalysts, and oxides of cobalt and nickel give lessselective catalysts.

A comparison of catalysts containing these latter active constituents isshown in the following Table A:

Table A Butene dehydrogenation at 2100 F.. lecd rate-4500 volumesbutene! One particularly effective catalyst of the above type includingthe promoter and the stabilizer has the following composition:

Parts by Component weight ZnO encn

The above catalysts may conveniently be prepared as follows:

' Example I 80ZnO20FezO3-5CllO-5K2O A solution of 259 grams of ferricnitrate [Fe(NO:)s.9H2Ol and 38.7 grams of copper nitrate [Cu(NO3)2.3H2O]in 1 liter of water was and mixed with a solution of 27.4 grams of KNO:

in 200 cc. of H20. The mixture was dried, heated for 3 hours at 1200 F.,and pilled.

A solution "of 262 grams of MnSO4.4HaO and 77.2 grams of Cll(NQa)2.3H2Oin 2 liters of H20 was stirred into a suspension of 539 grams of zincsubcarbonate [2ZnCO3.3Zn(OH)2l in 2 liters of H20. A solution of 228grams of K200: in 400 cc. of H20 was added and the solution heated for 1hour at 80-90" C. The precipitate was filtered, thoroughly washed, andmixed with a solution of 37.5 grams of KzCO: in 200 cc. of H20. It wasdried, heated for 3 hours at 1200 F. and pilled.

The above catalysts possess a high degree of selectivity to thedehydrogenation of normal butene to butadiene, the selectivity being ofthe order of 70-85%.

In order to set forth the utility of my invention, the followingdescription of tests in which butene-1 was dehydrogenated to formbutadiene when employing a zinc oxide base catalyst is set forth below:

Example III A mixture of normal butenes (containing about Over theZnOFeaOaCuO-K2O catalyst 44% of the butene was converted to otherproducts with 69% selectivity (30.4% butene to butadiene). The amount ofcarbon deposited on the catalyst was about .2%, and 4.1% of the butenewas converted to oxides of carbon (mostly carbon dioxide).

Example IV Under similar conditions the ZnOMnO2-CuO'-K2O catalyst gave38% conversion with 75% selectivity (28.5% of the butene converted tobutadiene) Only .3% of the butene was converted to carbon (deposited onthe catalyst) and 4.3% was converted to oxides of carbon.

If the temperature is lowered or the feed rate is increased so that thetotal conversion is reduced to a selectivity of 80-85% may be obtained.

In carrying out the process using catalysts of the type above described,the hydrocarbon. preferably with steam, is passed over the catalyst at arate between 50 and 5000, preferably between 100 and 1000 volumes(measured at normal temperature and pressure) of hydrocarbon'per volumeof catalyst per hour. The ratio of steam to hydrocarbon is between :1and 1:1, preferably from 8:1 to 4:1. The reaction chamber is maintainedat a temperature between 1000 and 1600 F., preferably between 1100 and1300 F. and

under atmospheric, below atmospheric or above atmospheric pressure. Thehydrocarbon which passes through the reaction zone unaffected may ofcourse be recycled thereto.

The principal function of the steam is to dilute the hydrocarbon andthus reduce the partial pressure thereof in the reaction zone. At thesame time, however, the steam performs another useful function in thatit reacts with coke which may be deposited on the catalyst to formcarbon oxides and hydrogen. The elimination of at least a portion of thecoke in this manner tends to prolong the time the catalyst can be usedbefore it requires regeneration. Thus the reaction portion of a completecycle of reaction and regeneration may be as long as 15, 25 or 50 hoursor more although it is usually preferable in operation to run forperiods of /2 hour to 10 hours and then regenerate.

Regeneration of the catalyst may be eiiected by shutting oil? the how ofhydrocarbon and passing steam, air, or a mixture of steam and airthrough the catalyst mass while it is maintained at a temperaturebetween 1100 F. and 1300 F. Following substantially complete removal ofcoke fromthe catalyst in this manner, the flow of hydrocarbon and steammay be resumed.

Mv present invention may be carried out either in the stationary bedtype of operation or a fluid catalyst type of operation. In the former,the catalyst is contained in a case or reactor, and the mixture of steamand hydrocarbon is simply, forced through the material, preferably beingdischarged into the top, forced through the catalyst, and withdrawn fromthe bottom. The catalyst is preferably in the form of pellets, pills,granules, and the like. In the fluid catalyst type of operation, thecatalyst is in the form of a powder having a particle size of from to400 mesh and is discharged into the reaction zone from a standpipetogether with the hydrocarbon to be dehydrogenated, and steam. thecatalyst and vapors entering preferably at a point at the bottom of thereactor and passing upwardly through a grid and that contact timeinterval forming within the reactor adense phase suspension, that is tosay, a suspension of catalyst in the gases of a concentration such thateach cubic foot contains from 2 to 35 or more lbs. of catalyst. Thisdense phase may be formed within the-reaction zone above the grid bycontrolling the linear velocity of gases or vapors by regulating themwithin the range of say /2 to 8 to 10 ft./sec. Continuity of operationmay be thus obtained and the catayst may be withdrawn through a bottomdraw-01f pipe regenerated, if necessary, and returned preferablysubstantially uncooled through the aforementioned standpipe to thereactor. The precise details, however, of operating the reactor do notform an important aspect of my present invention and any known reactoradapted to provide good contact'between the solid and gas may beemployed.

To recapitulate, my present invention relates to improvements ofdehydrogenation catalysts, to the methods of preparing such catalysts,and is characterized briefly by the fact that I employ a zinc oxide basein addition to oxides of iron, manganese, cobalt or nickel and a smallamount of a promoter and/or astabilizer. An outstanding advantage of myinvention is that I may carry out the dehydrogenation of a hydrocarbonin the presence of large quantitiesof steam without injuring thecatalyst and thusI may-greatly extend the life of catalysts since thepresence of steam tends to retard the. depositionlo'i, hydro- 7 carboncontaminants 'uponthe catalyst. 'Also;

the presence of steam makes itpossible'to supply 1 1 the heat necessaryforthis highly endothermic reaction by the superheatingof-the said steamat least in substantial part and-also makes it nos sible, particularlywith the stationary bed type of operation, to control-the contact timesince dilution with steain of the entering reactant makes it possible tovary-thereaction time virtually to any desired value regardless of howsmall maybe. What I claim is: 1. An improved dehydrogenation catalystconsisting of the following in parts by weight: ZnO, 80: Fe:0:,20:K:O,5: and CuO. 5.

2. A dehydrogenation catalyst consisting essentially or about -97 partsby weight of ZnO,

file oi this patent:

UNITED STATES PATENTS Number Name Date 1,986,241 a Wulfl. et al.. Jan.1,1935 [2,110,833 -1 Mark et al Mar. 8, 1938 2,239,000 Groombridge etal. Apr. 22, 1941 12,211,751; ,vVisser etaL- Feb. 3, 1943,

1,068,968 Bosch et a1: July 29, 1913. 2,148,140 'Tropsch Feb. 21,19892,180,672 Frey 1---... Nov. 21, 1939 2,184,235 Groll et al. 1..' Dec.19, 1939 2,216,131 Pieret al. Oct. 1,' 1940 2,265,641 Grosskinsky et al.Dec. 9,1941 2,315,107 Chickinoflf... Mar. 30,1943

7 I FOREIGN PA'IENTS Number Country Date 340,58? 'British Aug. 19, 1930524,918 British Dec. 30, 1930 141,016 Swiss Sept.'16. 1930 141,018

about 3-50 parts by weight of a metal oxide selected from the groupconsisting of FegOs, MnO and CrzOa, about 0.5 to 15 parts by weight ofan alkali metal oxide promoter and about 1-15 parts by weight of astabilizer preserving the activity of the promoter and selected from thegroup consisting of oxides of metals of the right hand side of group Iof the periodic system.

3. A dehydrogenation catalyst consisting essentially of about 50-97parts by weight of ZnO, about 3-50 parts by weight of FezOa, about0.5-15 parts by weight of an alkali metal oxide promoter and about 1-15parts by weight of a stabilizer preserving the activity of the promoterand selected from the group consisting of oxides of metals of the righthand side of group I.

4..Ihe catalystas claimed in claim the promoter is K20.

5. The catalyst as claimed in claim 3 wherein the promoter is K20.

' KENNETH K. KEARBY.

2 wherein the Swiss Sept. 13, 1930

